HV MOS Transistor Sub-Gate Mitigates Kirk-Effect
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional LDMOS transistor devices experience the Kirk-effect and high substrate current issues when operating at high voltages, leading to device burnout and limitations in achieving high voltage operations.
Innovation Solution
A sub-gate structure is electrically connected to the drain region and disposed between the drain region and a first isolation structure, partially on the first drift region, to reduce current injection into the depletion region and mitigate the Kirk-effect.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the gate voltage is increased to achieve higher breakdown voltage operations, then the voltage handling capability is improved, but the Kirk-effect and substrate current increase causing device burnout
Solution Approach 1:
The gate structure is divided into a main gate and a sub-gate, where the sub-gate is positioned between the drain and the main gate. This segmentation allows independent control of the depletion region, enabling the sub-gate to modulate the electric field and reduce substrate current while the main gate maintains high voltage capability.
Solution Approach 2:
The sub-gate acts as an intermediary element between the drain and the main gate, controlling the depletion region formation. By adjusting the sub-gate voltage, the electric field distribution is optimized to reduce Kirk-effect and substrate current, thereby protecting the device during high voltage operations.
2Reliability
If the drift region area is increased to handle higher voltages, then the breakdown voltage is improved, but the device area and complexity increase
Solution Approach 1:
The sub-gate is positioned locally in the drift region between the drain and the main gate, creating a localized control zone. This allows precise modulation of the depletion region only where needed, rather than requiring a uniformly large drift region, thus reducing overall device area while maintaining high voltage capability.
3Object-affected harmful factors
If the dopant concentration in the drift region is increased to reduce substrate current, then the Kirk-effect is mitigated, but the breakdown voltage capability decreases
Solution Approach 1:
Instead of changing the dopant concentration parameter in the drift region, the invention changes the electric field distribution parameter by introducing the sub-gate. The sub-gate voltage controls the depletion region width and shape, effectively reducing substrate current while preserving the low-doped drift region necessary for high breakdown voltage.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration allows for improved operation at higher voltages by reducing electrical current injection and avoiding vertical punch-through, enabling higher voltage capabilities without increasing dopant concentration in the drift region.
Implementation Method 1
the sub-gate structure at least partially disposed on the part of the first drift region disposed between the drain region and the first isolation structure may be used to lower the current injected into the depletion region during high voltage operations. The Kirk-effect problem may be improved
Data Source
AI summary
A high-voltage metal-oxide-semiconductor transistor device includes a semiconductor substrate, a gate structure, a first drift region, a first isolation structure, a drain region, and a first sub-gate structure. The gate structure and the first sub-gate structure are disposed on the semiconductor substrate and separated from each other. The first drift region is disposed in the semiconductor substrate and disposed at one side of the gate structure. The first isolation structure and the drain region are disposed in the first drift region and separated from each other. A part of the first drift region is disposed between the drain region and the first isolation structure. The first sub-gate structure is at least partially disposed on the first drift region disposed between the drain region and the first isolation structure, and the first sub-gate structure is electrically connected to the drain region.